Silicon oxide materials (such as, for example, silicon dioxide) are commonly used in semiconductor device fabrication as insulating materials. Silicon oxide materials can be formed by chemical vapor deposition (CVD) from appropriate precursors. An exemplary combination of precursors that can be utilized for forming silicon oxide materials is silane (SiH4) and hydrogen peroxide (H2O2). Another precursor combination which can be utilized for forming silicon oxides is tetraethyl orthosilicate (TEOS) and ozone (O3).
Silicon oxide materials can be doped with one or both of boron and phosphorous to alter (lower) a dielectric constant of the material. The boron and/or phosphorous can be introduced into a silicon oxide material by, for example providing one or both of a boron-containing precursor material and a phosphorous precursor material in a CVD reaction chamber during deposition of the silicon oxide material. Suitable phosphorous precursor materials include, for example, PH3 and tetraethoxy phosphine (TEPO). Suitable boron-containing precursors include, for example, B2H6 and triethyl borane (TEB). An alternative method of introducing phosphorus and/or boron into a silicon oxide material is to implant one or both of phosphorus and boron into the material.
A characteristic of a deposited silicon oxide material is its so-called flow temperature. A flow temperature is a temperature at which the silicon oxide material will melt. Flow temperature can be an important characteristic of silicon oxide materials. For instance, incorporation of silicon oxide materials into semiconductor fabrication processes frequently involves melting and reflowing of the materials to increase planarity and obtain good coverage of the materials over underlying device structures. Films consisting essentially of silicon dioxide typically have flow temperatures of about 1,100° C. or higher. Addition of boron or phosphorous to such films can reduce the flow temperatures to less than 850° C. It would be desirable to further reduce flow temperatures. Specifically, silicon oxide flow frequently occurs after provision of semiconductor devices in a semiconductor fabrication process. The high temperatures of silicon dioxide reflow can adversely affect such devices.
Another characteristic of silicon oxide materials is density. Denser materials generally have better flow properties than less dense materials. Specifically, denser materials can frequently reflow over underlying nonplanar structures more quickly than can less dense silicon oxide materials. Accordingly, it would be desirable to develop methods for densifying silicon oxide materials.